This project is designed to develop radioimmunoassays for the measurement of plasma levels of the tricyclic antidepressants. Tricyclic plasma levels vary widely among patients receiving the same dose of drug and the clinical response of individual patients may be related to plasma levels of the tricyclic. Present analytical methods are not suitable for the routine measurement of plasma tricyclics, whereas radioimmunoassay can be used for accurate measurement of large numbers of samples. The tricyclics for which radioimmunoassays will be developed including imipramine, desmethylimipramine, amitriptyline, nortriptyline protriptylone, doxepin, desmethyldoxepin and maprotiline. The radioimmunoassays developed will be tested for reliability, sensitivity and specificity and the results obtained will be tested against current methods.